When a network entity, such as a policy and charging rules function (PCRF), fails and/or restarts, the existing/ongoing user sessions may be maintained with no or minimal damage. This may be facilitated by the use of some kind of a recovery mechanism to restore the status and data of the ongoing sessions in the re-started network entity. When “hot redundancy” (i.e. every critical network entity is doubled, the second entity running active (“hot”) beside the first entity and maintaining the session statuses and data) is not used, at least some of the other network entities connected to the re-started entity may be involved, actively or passively, in restoring the session statuses and data in the restarted entity.
There have been considerations on restoration procedures for a network element. For example, restoring a pre-failure status of user sessions e.g. in the PCRF may be achieved e.g. by fetching the session status information and the related parameters from the network elements connected to the PCRF. Furthermore, restoration procedures may use protocols (e.g. general packet radio service (GPRS) tunneling protocol (GTP)) that comprise different planes (e.g. control plane, user plane) that separate the control and management functions from the user plane/user session functions.
FIG. 1 shows a general network scheme being a deployment scenario for a network element recovery scheme. Thus, FIG. 1 shows a communication system 100 that may comprise a user equipment (UE) (not shown) and a network (not shown). In turn, the network may comprise a policy and charging enforcement function (PCEF) 1021, a PCRF 1022, an application function (AF) 1023, a subscription profile repository (SPR) 1024, a bearer binding and event reporting function (BBERF) 1025, an online charging system (OCS) 1026 and an offline charging system (OFCS) 1027.
However, in case of failure e.g. of the PCRF 1022, a backup instance is required, such as PCEF 1021, AF 1023, or BBERF 1025. The backup instance already contains at least some session state information, and is used after the failure. In that case, the failed and restarted entity is up-dated/restored with the latest/up-to-date session information.
In consideration of the above, according to examples of the present invention, methods, apparatuses and a related computer program product for network element recovery are provided.
In this connection, the examples of the present invention enable one or more of the following:                Alleviating the need for load and dedicated support for the restoration measures in the network elements connected e.g. to the PCRF, i.e. in AF/P-CSCF, the gateways (P-GW, S-GW) and the subscription profile repository (SPR);        Avoiding mixing the network management issues within the user plane/user session related diameter protocols, if/when the restoration principles are applied to the PCRF interfaces, thus avoiding complicated, non-layered/non-modular specifications and implementations;        Keeping complexity low, i.e. implementations of network elements will not suffer from any extra complexity brought by the recovery and restoration procedures;        Avoiding network incompatibilities, if some network elements support the recovery and restoration extras and some do not or they support different mechanisms;        Providing information, on when and where a fatal failure and/or restart has taken place, to all entities involved in restoring the session statuses and data of a restarting entity;        Providing certainty about what exactly is expected from the involved entities and what triggers the actions; which party initiates the session recovery and how; what information does the restarted entity need from the counterparts;        Allowing re-binding of user and control sessions and control sessions related to each other and guaranteeing seamless operation/continuation of the ongoing user sessions by specifying how user/UE related control sessions used, with all protocol related details/parameters, between the restarted entity and the other counterparts are re-established/refreshed;        Coping with a restarting entity having lost all its session information, i.e. session statuses are restored from zero to the restarted entity;        Allowing recovery/restoration after failure/restart of a network element with a minimum impact on ongoing sessions and neighboring network elements and interfaces with simple implementations and loading minimized during the recovery/restoration, i.e. no loading peaks;        Allowing the entity having experienced failure and restart to find its former/pre-restart peer network entities.        